Pop Science: The Case for and Against the Soda Ban

Large soda bottles for sale at convenience store in Chinatown, March 11, 2013, in New York. A New York state judge halted a controversial ban on large sugary drinks in places that serve prepared food that was to take effect, March 12, 2013.

Mayor Michael Bloomberg says "the best science" is behind his controversial ban on large-sized sugar-sweetened beverages, which was overturned by a lower court earlier this week, but that doesn't mean all scientists agree.

"The best science tells us that sugary drinks are a leading cause of obesity," Bloomberg said Monday during a press conference to criticize the court's ruling.

New York Supreme Court Judge Milton Tingling took issue with Bloomberg's rationale, saying in part that lack of science was one reason for overturning the ban.

"The Board of Health may supervise and regulate the food supply of the city when it affects public health," and can do so when the city "is facing imminent danger due to disease," but that was not proven in this case, Tingling said in his written judgment.

So is the science on Bloomberg's side or not?

Sugary drinks are the single biggest source of calories in the American diet, providing more than 7 percent of daily calories on average, according to the Center for Science in the Public Interest. Statistics show both consumption of sweetened beverages and obesity rates have doubled since the 1970s.

Bloomberg's office released data Monday showing nine of the top 10 neighborhoods with the highest obesity rates city-wide were also the highest in sugary drink consumption. At the other end, the three least obese neighborhoods were also the lowest in sugary drink consumption.

While soda consumption has risen in lock step with an increase in the nation's collective waistline, that doesn't necessarily prove they are related, but an investigation published Monday in the American Journal of Preventive Medicine added to mounting evidence that they might be.

In the study of more than 10,000 children, researchers at the University of North Carolina in Chapel Hill found that sugar-sweetened beverages are the prime culprit responsible for higher caloric intake of children who consume them and are also associated with a higher intake of unhealthy foods.

"This is concerning because many foods that are associated with higher sugar-sweetened beverage consumption -- pizza, cakes/cookies/pies, fried potatoes, and sweets -- are also top sources of solid fats and added sugars," said lead investigator Kevin Mathias, a professor with the University's Department of Nutrition.

The science also indicates that size matters.

Besides the obvious fact that bigger sodas deliver a greater number of calories, studies show people tend to underestimate the amount of calories they've eaten and eat more when served heftier portions.

"The data clearly shows people who are given large portions consume more without realizing it and if you shrink portions they consume less but still feel satisfied," said Kelly Brownell, a professor of psychology and epidemiology at the department of health at Yale University.

As Brownell explained it, liquid calories in particular don't register with the brain in the same way calories from foods do, so people who drink copious amounts of sweet liquids take in a greater number of calories without feeling full.

In shrinking soda servings down from the current default container size of 20 ounces to a more "human sized" 16 ounces, Brownell said he thought most consumers would still feel satisfied even though they would wind up drinking less.

However, David Just, a professor of behavioral economics at Cornell University in Ithaca, N.Y., didn't support the ban based on different scientific criteria.

"We have good evidence that regular soda drinking puts on excess weight but we don't know what happens when we take it away or place limits. People may not drink less, they may not decrease calories, or they may replace it with something else equally caloric," he said.

Nearly 80 percent of soda and other sugar-sweetened beverages are sold in supermarkets, big box stores and convenience outlets, according to Beverage Digest; these types of establishments would not be covered by the Bloomberg serving size limits. Just said that because only restaurants, delis and movie theaters were shrinking soda sizes, the regulations would probably wind up targeting occasional rather than habitual soda-drinkers.

Executive director of Center for Science in the Public Interest, Michael Jacobson is a supporter of the Bloomberg initiative. He conceded that the initiative would have a modest effect on soda consumption and obesity rates at best, but he said that misses the point.

"It was a move in the right direction and should be considered as one part of a much larger strategy to limit the use of the only product demonstrated to cause weight gain," Jacobson said. "It's not a perfect measure, and it wouldn't solve all problems. But taken together with other regulations we've been lobbying for, like warning labels on soda containers and a limit on the amount of sugar a drink can contain -- and the soda industry is feeling the pressure."

Bloomberg, too, has also argued that the ban was one vital step of many in the war on obesity. He has vowed to appeal the court's ruling, highlighting the initial resistance to many of his previous initiatives that were met with initial resistance but ultimately accepted by the public. The addition of calorie counts on fast food menus and the elimination of trans-fats in restaurants come to mind.

"Already our proposal to limit the size of sugary beverages has changed the national conversation around obesity," Bloomberg said in a statement.

This may be true -- but with some unintended consequences. In Mississippi, a state where one in three adults is obese, the "Anti-Bloomberg Bill" has received bipartisan support and now sits on the governor's desk.

If passed, the law would bar counties and towns from enacting rules that require calorie counts to be posted, put a cap on portion sizes, or keep toys out of kids' meals.